1. Field of the Invention
The present invention is broadly concerned with processes for utilizing the enzymatic activity remaining in peptone solutions for carrying out various hydrolysis processes, as well as preserved mucosa tissue products and methods for preserving these products. More particularly, the mucosa tissue is hydrolyzed by conventional processes with an excess quantity of enzymes to yield a product comprising heparin (which is preferably extracted) and a peptone solution. A protein-containing material (e.g., soybeans, animal liver) is then hydrolyzed using the enzymatic activity remaining in the peptone solution. In another embodiment, the mucosa tissue is preserved by mixing the tissue with a preserving agent selected from the group consisting of hydrogen peroxide and phosphoric acid to yield a preserved product. The mucosa product preserved by hydrogen peroxide has a low ash count and reduced odor.
2. Description of the Prior Art
Peptone is a hydrolysate mixture derived from the mucosa tissue of swine, cattle, and other animals. Peptone is produced by hydrolyzing mucosa tissue with proteolytic enzymes to produce a digest solution containing, among other things, protein hydrolysates (i.e., peptone) and heparin. The heparin, which has great commercial value, is then extracted from the digest solution, typically by anion exchange resins. These processes and the resulting products have been described in U.S. Pat. No. 5,607,840 and GB 992,201, incorporated by reference herein.
When hydrolyzing mucosa tissue, large quantities of proteolytic enzymes are used in order to increase the heparin yield. For example, during mucosa hydrolysis, proteolytic enzymes are typically added at a rate of about 1–1.5 g of enzyme per kg of mucosa tissue. This is equivalent to about 13–20 g of enzyme per kg of protein present in the tissue as compared with about 0.2–3 g of enzyme per kg of protein utilized in other hydrolysis processes. Such large quantities of enzymes increase the costs of carrying out these processes and results in a substantial amount of enzymatic activity remaining after these processes have concluded. This activity is then deactivated by lowering the pH of the product (which is reversible) or by irreversibly denaturing the enzyme with heat. There is a need for a process which would provide commercially viable uses for this excess enzymatic activity.
There are numerous protein-containing materials which are hydrolyzed for various purposes which could benefit from this excess enzymatic activity. For example, soybeans are an inexpensive source of essential amino acids. However, anti-nutritional factors such as protease inhibitors and antigenicity are also present in soybeans. These factors can be substantially reduced by hydrolyzing the soybean proteins. Similarly, whey proteins are an important source of proteins for young animals, but whey proteins have a drawback in that they may cause allergic reactions. This risk of reaction can be reduced by hydrolyzing the whey proteins. Finally, enzymatic hydrolysis processes have other useful purposes, including reducing the viscosity of blood products, increasing the bioavailability of feed-grade meat isolates, and increasing the quantity of soluble materials which can be extracted from by-products such as fish offal.
On a dry basis, typical peptone derived from heparin production processes includes about 50–55% by weight crude protein and about 20–30% by weight ash. Due to this protein content, peptone is commonly used as a nutritional supplement for animals. However, currently available peptone suffers from two disadvantages—a high ash level and an unappealing flavor. High ash contents in peptone have been shown to adversely affect animal weight gain (see e.g., Journal of Dairy Science, Vol. 75(1):267 (1992)). These high levels are predominantly caused by the current mucosa preservation methods wherein sodium metabisulfite or calcium propionate is added to the mucosa product or wherein the pH of the product is lowered. There is a need for a mucosa preservation method which is effective yet does not generate high levels of ash in the resulting peptone solution, thus reducing the unappealing flavor in peptone.